The number of NYPD recruits dropping out of the Police Academy has skyrocketed since the department lowered its starting salary, further thinning the already-shrinking ranks of New York’s Finest.

Police statistics show escalating double-digit losses at the academy with every class since the city reduced the police starting salary in January 2006 to a puny $25,100 – a level set during bitter arbitration between the cop union and city.

In fact, the so-called “fall-off” figure of would-be cops – who flunked, were dumped or quit for greener pastures – reached a historic 20 percent just two months ago, when the NYPD graduated a paltry 914 officers out of a class that started with 1,142 recruits.

That translates into one out of every five recruits never making it onto the streets, putting further pressure on filling gaps throughout the NYPD’s various “Impact Zones” and other police units that have recently come to rely on new rookies, officials said.

The disturbing trend of prospective cops falling by the wayside has continued in the present class, with 1,217 wannabe cops already losing about 150 recruits, or 13 percent.

In contrast, the last class of recruits paid at the higher, $40,000 salary in July 2005 had a “fall-off” rate of just 11.8 percent, with 1,968 recruits entering the class and 1,736 completing its academic and physical rigors.

And it’s not just a problem of keeping the would-be cops – the department can’t recruit enough potential candidates in the first place, officials say.

The problem of filling academy classes has been so significant that the NYPD recently could not attract enough recruits to fill 800 vacant spots – which allowed Police Commissioner Raymond Kelly to proclaim at a City Council hearing that the department could accept another round of budget cuts by slashing 1,000 slots he could not fill in the first place. Kelly said the “primary reason” that academy recruits drop out is money.

“They didn’t realize how low [the starting salary] was. They saw what it re sulted in a check every two weeks, and they de cided they are going to go elsewhere.”

A spokesman for Kelly said the “drastic decreased pay and tough academic standards” are responsible for the slide.

The NYPD has shrunk from a pre-9/11 high of 41,000 to 36,000, a level not seen since 1993.

Patrick Lynch, president of the Patrolmen’s Benevolent Association, said the overall pay structure for cops is too low, forcing the NYPD to “take anyone with the barest of qualifications” and lacking “the drive and dedication it take to make it in the NYPD, and they drop out.”

Police officials insist they are not compromising standards and say their inability to get enough recruits show they are not reducing values to get them.